Potentiometric and spectroscopic study of mixed-ligand copper(II) complexes with N,N,N′,N″,N″-pentamethyldiethylenetriamine and α- (or β-) alaninehydroxamic acids in water solution

Abstract Stabilities of the mixed-ligand complexes of Cu 2+ ion with N , N , N ′, N ″, N ″-pentamethyldiethylenetriamine [ N , N , N ′, N ″, N ″-pentamethyl-{bis(2-aminoethyl)amine}, Me 5 dien] as a primary ligand and α-alaninehydroxamic acid [2-amino- N -hydroxypropanamid, α-Alaha] or β-alaninehydroxamic acid [3-amino- N -hydroxypropanamid, β-Alaha] as a secondary ligand L and their absorption and EPR spectra at various pH values are reported. The visible spectra exhibit a characteristic red shift and a shoulder at lower energies indicating a five-coordinate structure of the formed complexes. The change of the EPR spectral parameters as a function of pH reflects two modes of an equatorial–axial chelation by the aminohydroxamic acid ligand L in the [Cu(Me 5 dien)(HL)] 2+ and [Cu(Me 5 dien)(L)] + species.